Anaplastic carcinoma of the thyroid with chondroblastoma features mimicking papillary carcinoma: a case report.

Background: An unusual case of anaplastic carcinoma of the thyroid arising from a metastatic focus of papillary carcinoma.

Case: The tumor affected a 69-year-old woman with a history of total thyroidectomy for papillary thyroid carcinoma 4 years previously. She presented with a rapidly enlarging neck mass that histologically simulated chondroblastoma. A small, embedded focus of residual follicular variant of papillary carcinoma was present. The patient died of disease 3 months later.

Conclusion: This "chondroblastoma" variant of anaplastic thyroid carcinoma has not been reported to date.